In industries where performance, safety, and reliability are non-negotiable, magnet testing and quality control are critical to ensuring consistent and compliant magnetic components.
Quality assurance (QA) goes far beyond checking basic pull strength and is vital for the safety of the manufacturer and end user – no matter what you’re sourcing magnets for, be it for electric motors, sensors, medical devices, or industrial assemblies. QA involves material validation, dimensional precision, magnetic performance, and long-term stability, all of which must align with both functional requirements and regulatory standards.
In this article, we’ll explore the key principles, methods, and best practices behind magnet testing and quality control, helping engineers and procurement professionals make informed decisions.
Why Magnet Testing Matters
Permanent magnets, especially neodymium (NdFeB) and samarium cobalt (SmCo), are used in critical applications, such as in EV drivetrains and aerospace actuators. Even the smallest of variation in the composition, orientation, or coating could lead to:
- Reduced magnetic output
- Demagnetisation under temperature or load
- Mechanical failure due to brittleness or corrosion
- Compatibility issues in assemblies or automated processes
Implementing robust magnet inspection protocols at the manufacturing or incoming QC stage is essential to avoid costly downstream failures.
Key Quality Control Checks for Magnets
Here are some of the most important testing categories used to evaluate magnetic components:
1. Magnetic Property Testing
Testing the core magnetic characteristics of the magnet ensures it meets design performance.
- Br (Residual Induction) – Indicates maximum magnetic flux density the material can produce.
- Hc (Coercive Force) – Resistance to demagnetisation, critical for motors and high-temperature use.
- BHmax (Maximum Energy Product) – Overall magnetic performance; higher = stronger magnet per unit volume.
Best Practice: Use a Hysteresis Graph (BH Tracer) or Fluxmeter to verify magnetic values per batch.
2. Dimensional & Tolerance Testing
Precision is essential, particularly when magnets are part of tight-tolerance assemblies (e.g., sensors or brushless motors).
- Use digital callipers, coordinate measuring machines (CMMs), or laser scanners for shape and size validation.
- Confirm squareness, concentricity, and flatness where required.
Pro Tip: Even small dimensional shifts can impact magnetic circuit behaviour and fit.
3. Coating Integrity & Corrosion Resistance
Most neodymium magnets are typically coated with nickel or epoxy to protect against corrosion and oxidation.
- Salt Spray Testing is commonly used to simulate long-term exposure to harsh environments.
- Adhesion and thickness tests ensure the coating remains effective under mechanical stress.
4. Temperature Stability & Aging Tests
Magnets degrade over time, especially under elevated temperatures.
- Conduct thermal cycling to observe stability under fluctuating temperatures.
- Measure magnetic flux before and after exposure to test thermal reliability.
- For critical use cases (EV motors, aerospace), magnets should be rated for 200°C+ and tested accordingly.
5. Polarity and Magnetisation Direction
Incorrect polarisation or magnetisation angles could result in part rejection or malfunction.
- Use Gaussmeters or Helmholtz coil testers to verify polarity and field direction.
- Especially important for multi-pole magnets, magnetic arrays, and Halbach configurations.
In-Process vs Final Quality Inspection
High-reliability industries require both in-process controls (at magnet manufacturing stage) and final acceptance testing at the point of assembly or integration. Best-in-class suppliers will provide:
- Batch traceability
- Full test reports and certificates
- PPAP or First Article Inspection (FAI) documentation
- Custom test protocols tailored to your specific requirements
What to Ask Your Magnet Supplier
When evaluating magnet suppliers or auditing quality processes, consider the following:
- Do they test 100% of their magnet products?
- Can they provide material certifications and ROHS/REACH compliance?
- Do they have in-house testing facilities, or rely on third parties?
- Can they customise QC based on your industry or regulatory standards?
Partnering with a supplier who understands the application-critical nature of magnets can reduce risk, lower failure rates, and ensure long-term product integrity.
Magnet testing and quality control are not one-size-fits-all. That’s why our expert team is here to support engineers, manufacturers, and designers with:
- Rigorous in-house testing
- Custom magnetic assemblies
- Application-specific advice
- Full traceability and documentation
Contact our team today to discuss any questions you might have or for support with your particular application.
